few utils features 

Hello I'm Matthieu and I implemented your library in keystoneJS project api (keystone cms only implement a "cloudinary" image type, and i needed a traditional server image uploader) . Unfortunately I had to make few changes in order to make it work. Therefore, it would be awesome to update this node module with my changes.

Sorry I just copied the whole content of my working repo, but it's all the same with few changes, and everything seems to work perfectly. 

cheers ! 

"added uploadFile function to be able to upload a file without passing by formidable parsing, added config json object to be passed as argument option + remove some files by passing a variant object"